What started out as a journey to better understand regulatory T cells has now led to an intriguing approach with an investigational cell therapy designed to prevent the risk of graft-versus-host disease and to improve relapse-free survival rates in patients undergoing hematopoietic stem cell transplantation.
What started out as a journey to better understand regulatory T cells has now led to an intriguing approach with an investigational cell therapy designed to prevent the risk of graft-versus-host disease (GVHD) and to improve relapse-free survival rates in patients undergoing hematopoietic stem cell transplantation (HSCT).
Data of a phase 1/2 trial recently showed that the first-generation precision cell treatment Orca-T compared with a historical control of standard HSCT demonstrated faster neutrophil (median, 12 days vs 14 days; P < .0001) and platelet engraftment (median, 11 days vs 17 days; P < .0001), decreased incidence of grade 2 or higher GVHD at 100 days (10% vs 30%, P = .005) and chronic GVHD at 1 year (3% vs 46%, P = .0002).1,2
The 1-year GVHD-free and GVHD relapse-free survival (GRFS) rates were 75% with the use of Orca-T vs 31% with standard HSCT (P < .0001). The comparator cohort was derived from contemporaneous patients who had been treated at Stanford University with a conventional allograft.
Along with feasibility of the approach, the results also highlight how Orca-T demonstrates potent anti-leukemic activity in patients who have active disease at HSCT, which suggests that the decrease of GVHD does not impact graft-vs-leukemia (GvL).
“That is the most exciting part about the Orca-T story; it is the ability to do this with precision, with speed, and to export it to other sites. The results are intriguing, and very supportive,” said Robert Negrin, a professor of medicine (blood and marrow transplantation), and chief of the Division of Blood and Marrow Transplantation at Stanford University.
In an interview with OncLive, Negrin, who is senior author on the trial, shared the evolution of Orca-T as a novel approach to HSCT, highlighted his robust experience with using this cell therapy at Stanford University, and how Orca-T is a potential prevention method for GVHD.
OncLive: Please provide some background to this therapeutic approach. What is the mechanism of action? How is it effective in patients undergoing transplant?
Negrin: This whole idea came from mouse studies many, many years ago, where we identified GVHD as being a dysregulated immune reaction that just keeps going, and going, and going. Like you and I, when we react to something, we have a reaction—let's say, influenza. Our body responds, and then we stop reacting and you get better. With GVHD, what we noticed in using a bioluminescent animal model is that the alloreactive T cells just keep going, going, and going and are unrelenting in mice, just like in people. The problem is very similar and affects certain organs in a very similar way.
Therefore, we went about trying to understand the use of so-called regulatory cells. These are cells that everybody has that help control immune reactions. We just applied them in this clinical scenario, first in mice work done by Matthias Edinger, MD, when he was a postdoctoral fellow many years ago [and other researchers]. All of them were very actively involved in these studies, and showed, somewhat surprisingly, that the administration of regulatory T cells could control this dysregulated immune response that we called GVHD.
Probably more surprising was that, at least in the animal models, it also allowed for the benefits of transplant, namely, the graft-vs-tumor effect and better immune recovery. This was in large part because GVHD also impacts the immune repertoire and where the immunity is developed in the recipient.
All of this was very nice in mouse models and was very elegant. We did a lot of studies, published a number of nice papers, and thought this would be a great idea because it sort of solved, or at least addressed, the principal problems after bone marrow transplantation—namely, avoidance of GVHD yet retention of graft-versus-tumor effects and better immunity. A lot of times, people say, "Oh, that sounds good in mice, but, that's too good to be true." And, they’ll ask, "Will that all work in people?"
Where did the biggest challenges lie in this approach?
The big challenge came about to try to apply this to patients. We also have one other interesting point that is relevant. If we gave the regulatory T cells first, before the so-called conventional CD4+/CD8+ cells, that allowed for a lower dose of regulatory T cells. This is because a big challenge is the paucity of these cells; you and I don't have that many.
Then, the other big challenge was the technical ability to isolate in cells. What we do in mice is cell sorting, which is a standard technology. But, that was not developed in people because we're big—there are a lot of cells, and cell sorting is rather slow, and it's very specific. To get enough cells takes a really long time. It's somewhat of a heroic thing to do in people, to get the adequate amount ourselves; of course, we don't really know what this proper cell dose is.
However, what we thought we learned was that the ratio of conventional to regulatory T cells was the key component. Also, if you give the regulatory T cells first, you can get fewer numbers. Those are things you can do in transplant. You can get the cell from the donor, and you can give cells in a certain sequence; all of those things are very doable. It seemed like an attractive thing to do in patients.
Then, the question was: Does it work? There are 3 groups that have really pioneered this work. The first study came from the University of Perugia in Italy. They did this in haploidentical transplantation; you cannot avoid immunosuppression in haploidentical transplants. They were able to show in several nice papers that you could do this strategy, and seemingly, get away with low risk of GVHD, and also low relapse. This is because the other issue is: how do you measure the graft-vs-tumor effect? There is no assay, and we have no test; you have to wait and see who relapses and who doesn't. Therefore, they also showed rather convincingly that you could reduce GVHD risk, yet, there was a very low risk of relapse in their high-risk patient population. Those were very important [data].
Another study from the University of Minnesota did this with umbilical cord blood. They expanded the regulatory T cells from a third cord blood unit, which is somewhat heroic—it is another level of complexity to isolate the cells and then expand them. We did this in matched donors—either matched siblings or matched unrelated donors. We published a paper in JCI Insight several years ago showing the initial results, and they look quite favorable.
Therefore, what I think is most exciting about what Orca Bio has done is they are developing technology to isolate the cells more quickly, to be able to do this on a clinical scale, with precision, and with speed. Also, [they are developing the technology] to be able to distribute it to anybody, because the criticism of all these studies is that, "Oh, that's nice. But, this is a single-institution study. Is this really true? Can this be exported? Could this be something that [an organization] other than these [individual] centers are really focused in this area and have developed these technologies could really do?” Orca Bio is developing the technology, and improving the technology, because it's still very cumbersome, and exporting the technology so that you could do this, theoretically, at any center.
That's what I think is most exciting about the Orca Bio abstract; it is demonstrating that this can be done. It certainly opens the door to prevention of GVHD. As we move into an era of using cell-based therapeutics, now, this opens up many other possibilities, because you use these regulatory cells and autoimmune disorders and organ transplant tolerance. There are many other cell types that have potential clinical utility, but getting them, and purifying them, is a big challenge. There are many other possibilities that one could think of.
Obviously, more time will be required to follow these patients, but they certainly are supportive of the idea that you can improve overall outcomes using this strategy. That's what we hope to be able to demonstrate further.
Please focus on the scalability of this approach. Through these types of collaborations, how do you see Orca-T potentially moving through the FDA pipeline?
In academia, we don't develop drugs. It's too much, we don't have the resources, we don't have the capability, and we don't have the monitoring capability that is required for multi-institutional studies. Where these commercial partners come in is, they can raise money for interesting concepts, which Orca Bio has done, and they can export this to other centers, and that's critically important.
As we've seen in the CAR T-cell [therapy] world, that can be a quite successful commercial business. Also going through the process of an FDA approval—which Orca Bio is moving along in that process—and getting the right designations is critically important to commercial entities. In academia, it's important to us, but that's just not our focus.
We don't have the resources around, the people and the expertise to really drive things through that process. We're good at developing the studies and getting FDA approvals, and [investigational new drug applications], but not really [good at] developing drugs as a commercial entity. This collaboration is key to doing this successfully; for example, at Orca Bio, [they have] technology to separate cells more efficiently and effectively. They also have the resources to do a multi-institutional clinical trial, and the expertise to move something through and present it to the FDA. Those are key components.
Could you expand on the study and respective data from this phase 1/2 trial?
Here at Stanford Cancer Institute, we did find in our patients that giving low doses of immunosuppressive medications with a single agent seem to improve the outcomes, and it's remarkable how well these patients have gone through the transplant. It's a little bit hard to appreciate an abstract until you take care of these patients, and many of them just sort of move to the transplant with relatively little challenges. We have not seen greater risks of things like infection [or] disease recurrence; those are obviously things that will be followed.
When we look at the 1-year GVHD relapse-free survival rate, which is an endpoint that most transplant studies would agree is the most important end point, the overall outcomes are much more favorable compared with a historical control group.
The data are very encouraging, and the overall outcomes look very strong in a reasonable number of patients now. We think it's important for the community to hear about it, and to get it on everybody's radar, and be excited about trying to move this forward as a more standard therapy. This is still a clinical trial, so it's not, it's not part of any standard therapies yet. We are using this quite regularly and have been very encouraged by the ease of which patients go through the transplant. It's still an allogeneic transplant; there still are many challenges there. However, these patients seem to be doing quite well, we're very encouraged, and so we keep going.
How does this approach impact patient outcomes as it relates to quality of life (QoL)?
The hard end points of 1-year relapse-free survival is obviously the most important to patients. However, going through an allogeneic transplant is obviously an incredibly difficult thing. Fortunately, I've only seen it [from] the doctor side, not [as a] patient.
However, I've seen many, many patients, and the quality of their life as they go through this experience is very important to all of us. As we saw these patients go through these studies, we felt like we were capturing something that was really important, and that is the ease [at which] many patients went through this experience, which just seemed different. It's hard to capture that.
It's really important for patients to speak and, and the way patients speak is in different ways. One way is through the QoL measures that they answer. This is [what they find] important, this is what they experienced—not what we say is happening. That's really important to hear that voice too. Those are data we're trying to collect. It's not so easy, because going through a bone marrow transplant is a poor QoL for everybody. But, by just to trying to capture this, [Orca-T seems] better than what we what we thought.
How has this changed the mindset of cell-based approaches in the community?
What has changed is the belief in the concept of cell-based therapies. A lot of these things are somewhat fanciful. It is also important to show that we can translate from an animal model [to a human]. There is a lot of criticism of animal modeling, because people say, "Well, it's nice for animal models, but it doesn't really translate into the clinic." Actually, my view is that because we don't actually follow the animal models, there are many compromises one needs to make. When you translate studies from animals to humans, there are many differences, and it's really important to try to follow them as carefully as you can within the limitations of what is possible. We were very engaged in that and tried to follow as carefully as we could. To me, that is very encouraging—that you can study things in animals that generate new concepts and be able to translate that into a clinical trial.
Obviously, with all of the caveats of an early-phase clinical trial, more time needs to pass, more patients to be treated, and you need to export [the treatment] to other centers. That's a really important point, because there are many things that get lost because, "it's too complicated. It's too expensive. People can't do it." I don't think anybody can do high-speed cell sorting, as a clinical project in a standard or standard cell-processing laboratory. It's above the level of what most processing laboratories can do.